1. Field of the Invention
The present invention relates to a method of processing data in a portable terminal device, and more particularly to a method of processing externally supplied data by a CPU in a non-operating state and a portable terminal device for the same.
2. Description of the Related Art
In the field of portable terminal device, a portable wireless terminal device using a wireless signal as the medium of data communication is conventionally known. In the conventional example, the internal structure of the portable wireless terminal device is divided into an information processing unit and a wireless interface unit which are respectively controlled by different CPUs. In this case, the CPU in the information processing unit is in a non-operating state from an energy saving viewpoint. That is, the supply of power to the CPU or the supply of a clock signal to the CPU is stopped. For this reason, the CPU is in the non-operating state. When a wireless signal is received by the wireless interface unit in a reception waiting state, a signal receiving process is performed. In this case, since it is necessary to start the CPU in the information processing unit during the signal receiving process, the CPU in the information processing unit is switched from the non-operating state to an operating state.
As a method of switching the CPU from the non-operating state to the operating state, the following methods are known.
1) An interrupt system:
This method is most general. In the method, only a signal detecting circuit on a controlled side is set to the operating state, and when a signal from a controlling side is detected, an interrupt signal is issued to the signal detecting circuit. Then, a main power supply is turned on and the CPU is set in the operating state.
2) A direct memory access (DMA) transfer system:
This method is described in, for example, Japanese Laid Open Patent Disclosure (JP-A-Heisei 2-244312). Serial communication data is transferred to a memory on a controlled side by direct memory access without passing through a CPU in the non-operating state on the controlled side.
3) A coil transfer system:
This method is described in, for example, Japanese Laid Open Patent Disclosure (JP-A-Showa 63-246935). A sync signal receiving coil is provided on a controlled side to receive a sync signal used to perform a serial communication. The sync signal of the serial communication data is received from a controlling side through the sync signal receiving coil, and the data communication is performed in synchronous with the received sync signal.
4) A command transfer system:
This method is described in, for example, in Japanese Laid Open Patent Disclosure (JP-A-Heisei 4-325842). A power supply controlling side issues an turn-on command for turning on a main power supply through serial data communication paths of a LAN and so on. Each of controlled sides receives and interprets this command by a serial data receiving unit and controls a main power supply via a power supply control unit. Thus, all the main power supplies of remote communication apparatuses on a controlled side are collectively turned on.
In addition to the above conventional example, various types of techniques of data transfer are described in a magazine "Transistor Technique" (1994, March) published from CQ Shuppan. In the described techniques, however, the circuit structure requires an expensive part or becomes more complicated for communication between the information processing unit and the wireless interface unit.
In the interrupt system of the above-mentioned conventional systems, the interrupt signal is issued to the CPU on the controlled side such that a main power supply is turned on. For this reason, there is the following problem. That is, even if data is sent from the wireless interface unit to the information processing unit, there is a case that the data cannot be correctly received depending on the timing when the CPU in the information processing unit is switched from the non-operating state to the operating state.
In the DMA transfer system, it is necessary that the serial communication unit and the reception memory are always in the operating state to allow the serial communication unit to receive the serial data through the DMA transfer. Also, a clock signal is required to be supplied to the serial communication unit. Therefore, there is a problem in power saving.
In the coil transfer system, in order to start the CPU in response to the reception of the sync signal by the coil such that the serial communication is performed, it is necessary to prepare the structurally large-scaled coil which can flow current sufficient to start the receiving circuit. For this reason, this coil transfer system is not suitable for the portable wireless terminal equipment which requires a compact size.
In the command transfer system, the power supply control unit is turned on at least to control the main power supply on the controlled side. As such, the power saving is not considered in the section. This is the most important problem in the portable terminal device driven with a cell.